N_Port ID Virtualization (NPIV) is a feature of Fibre Channel that provides the ability to report more than one entity (address) behind a lesser number of addresses.
However, the SAS protocol, including the new SAS-2 protocol, the specification of which is currently available in draft form (Revision 12, Sep. 28, 2007) at www dot t10 dot org and identified as T10/1760-D or Reference Number ISO/IEC 14776-152:200x, the contents of which are incorporated by reference herein, does not provide NPIV functionality, because SAS defines a Phy as representing a single SAS address. In other words, every end-device (represented by a Phy) has one and only one SAS address attached. Thus, a device attached to the Phy cannot differentiate more than one source or destination.
A SAS expander can generally be described as a switch that allows initiators and targets to communicate with each other in a network, and allows additional initiators and targets to be added to the network. There is a need to provide NPIV-like functionality within a SAS expander.